Conventionally, in one type of stators for electric rotary machines, coils are fabricated by winding windings around teeth of a stator core. In another type of stators, coils are formed by inserting plural segments each made up of an electric conductor which is formed into a U-shape using segment coils in slots in a stator core, and thereafter bending leg portions and connecting end portions of the segments (refer to JP-2003-158840-A and U.S. Pat. No. 6,894,417-B, for example).
However, for winding windings around teeth of a stator core to fabricate coils, expensive exclusive devices such as a winding machine or an inserter are required.
In JP-2003-158840-A and U.S. Pat. No. 6,894,417-B, the coil is formed by forming the electric conductors into the U-shape, bending the leg portions and connecting (welding) the end portions of the segments together. The same number of electric conductors as the numbers of turns of the windings and pairs of poles need to be prepared, and as the numbers of turns of the windings and pairs of poles increase, the number of manhours to be spent for the forming, bending and connecting work increases. Moreover, each of the forming, bending and connecting work is executed for each electric conductor. Thus, it could be further optimized in view of production efficiency.
On the other hand, these electric rotary machines are heated as a result of operation, and therefore, have to be cooled by means of air cooling, water cooling, oil cooling, etc.
In an air cooling, heat is dissipated into the air from heat dissipating fins which are provided on a housing of an electric rotary machine, and the resulting cooling performance is not so high. In electric rotary machines which are installed in motor vehicles, from the reason that a high cooling performance can be attained by cooling coils directly, an oil cooling may be adopted in which, for example, an insulation oil such as an ATF is sprayed directly to a stator and/or a rotor of the electric rotary machine so as to cool them. However, in the oil cooling, the reduction in insulation properties may be caused by water contained in the insulation oil, copper may be attacked by the insulation oil, and the torque of the rotor may be lost by virtue of viscosity resistance produced by the insulation oil.
In a water cooling in which, for example, the electric rotary machine is cooled via the stator core, the heat dissipating path may become long and the heat resistance may not be suppressed. Thus, a desired cooling performance may not be obtained. Additionally, in another type of water cooling in which a water jacket is disposed at coil spanning portions, the similar problem may be caused due to a small contact area with conductors.
Moreover, in the conventional electric rotary machines in which the coils are fabricated by winding the windings around the teeth of the stator core, the winding operation becomes complex and troublesome since the windings are wound while inserting insulation papers so as to be held between the windings so wound, and thus, the insulation paper may be caught between the winding wound, whereby a proper insulating performance cannot be ensured.
In JP-2003-158840-A and U.S. Pat. No. 6,894,417-B, since the U-shaped electric conductor is inserted in the slot after the insulation paper is inserted therein, the electric conductor may come into contact with the insulation paper when the electric conductor is so inserted, and the insulation paper may be caught between the electric conductor and the slot, whereby a proper insulating performance cannot be ensured.
Further, in the conventional electric rotary machines, since an insulation coating material such as enamel which is coated on the winding is used at least partially, it could be further optimized in view of the insulation performance.